That's a pretty naive point of view. Tons of people here are flipping, this guy is just doing it obviously enough for you to notice.
Russian sellers on this very thread are paying ~$20 per copy of XCom and selling them for 30+. Same with those cheap copies of Black Ops II which have been floating around for the past few months...
Hell, every other trader here is selling CD keys they paid almost nothing for through indie bundles (which are non-transferable by the rules which they bought the CD keys under).
I doubt many people here are actually selling stuff at cost. That only covers a small part of the trading market.